Influences of alloying elements on microstructure and tribological properties of a medium-weight high-entropy alloy

Abstract

In this work, individual influences of Al, Fe and Ni on the microstructure, wear resistance and mechanical properties of high-entropy alloys (AlxCrFeyNizTi0.2) were studied. Microstructures and phase constituents of the alloys with different values of x, y and z were characterized via Scanning Electron Microscope, Energy Disperse Spectroscopy, and X-ray diffraction. Mechanical properties and wear resistances of the alloys were evaluated, including hardness, micro-hardness, and resistance to abrasive wear. It was shown that with increasing Al content, the FCC phase was replaced by disordered BCC (A2) and ordered BCC (B2) phases, leading to an increase in micro-hardness by ∼73% and a decrease in wear volume loss by ∼78%. Fe also increased the fraction of A2 phase, but reduced hardness by ∼41% and led to a considerable decrease in wear resistance. In contrast, Ni helped form a FCC phase, resulting in a decrease in hardness by ∼35%, and an increase in wear volume loss by ∼73%. Abrasive wear appeared to be the dominant wear mechanism, while the formed oxide scale played a role in improving the wear resistance. Efforts were made to correlate the changes in hardness and wear resistance with changes in microstructure. Among all specimens, AlCrFeNiTi0.2 and Al0.5CrNiTi0.2 reached the highest wear resistance. The results obtained help shed light on the development of advanced wear-resistant high-entropy alloys via the favorable addition of Al.